Shadow of the Colossus takes place nearing the edge of the known world, in an area known only as "The Forbidden Land". It is here that a demon (or god of sorts), known as Dormin, resides. Dormin, having the power to bring back the dead, is approached by the protagonist, Wander, who makes a deal with the entity. If Wander slays sixteen colossi who roam the lands, Dormin will revive a girl, known as Mono, whose body Wander carries with him.
However, these colossi are living mountains, for the most part. In fact, several are literally hundreds of feet tall. Faced with these sorts of foes, Wander seems almost destined to lose horribly. At least, that would be the case if the colossi did not have one major weakness: their seals. Ancient seals are carved in to the flesh of these creatures, which, if stabbed with the blessed sword that Wander carries, serve as their Achilles Heel. The goal is simple: climb the colossi, locate their seals, and slay them, one-by-one.